An integrated memory is a memory formed on a semiconductor chip, also known as an integrated circuit. A memory takes the form of a matrix of cells connected to a matrix of orthogonal wires. Typically, among these wires there is a set of orthogonal wires serving to asdress each cell. A cell is addressed by means of two decoders, which respectively designate two orthogonal wires representing the line and column to which the cell is connected.
The invention relates to random access memories or RAMs. In these memories, data may be written or read at random. Consequently they have not only addressing wires but also a set of orthogonal wires that respectively enable storing a data bit in each of the cells and reading the contents of each cell. These wires are connected to a control logic that is subject to the action of a control signal CS and a read-write signal R/W that by its state dictates the reading or writing of data. The control logic includes an input for the data to be written into the memory and an output for the data read by the memory. All the information contained in a RAM is lost if the supply voltage disappears.
Among random access memories, a distinction is made between dynamic and static memories. The invention relates to static MOS-type memories, in which each cell contains a bistable multivibrator of a MOSFET (metal oxide semiconductor field effect transistors) type. The two states of the multivibrator represent the two values 0 and 1, respectively, of a data bit.
One advantage of static RAMs is the ability of switching rapidly from one state to the other. Nevertheless, static RAMS have a major disadvantage of requiring a large surface area to embody a cell. Until now, the structure of a bistable multivibrator has necessitated two MOS transistors, each being provided with a load resistor, while two addressing transistors must be provided, the conduction of which indicates which cell has been selected. Accordingly, the bulk of each cell cannot be reduced unless the geometrical dimensions of the transistors are reduced and they are assembled carefully.